JP2012008449A - Zoom lens and imaging apparatus having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens that has a satisfactory optical performance over the entire zoom range from a wide-angle end to a telephoto end while achieving an increase in zoom ratio and a reduction in the effective diameter of a front lens.SOLUTION: The zoom lens includes a first lens group of positive refractive power, a second lens group of negative refractive power, a third lens group of positive refractive power and the subsequent group including at least one lens group. When zooming takes place, the first lens group moves toward an image side while generating a convex locus. An interval between the first and second lens groups is wider at the telephoto end than at the wide-angle end. The second and third lens groups move so as to decrease the interval between the second and third lens groups. In such a zoom lens, the third lens group has at least one positive lens and at least one negative lens. The imaging magnifications β2w, β2T at the wide-angle end and telephoto end of the second lens group, the imaging magnifications β3w, β3T at the wide-angle end and telephoto end of the third lens group, the focal distance f2 of the second lens group, and the focal distance fT of the entire system at the telephoto end are appropriately set respectively.

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same, and is particularly suitable for a digital still camera, a video camera, a TV camera, a surveillance camera, a silver salt photography camera, and the like.

  In recent years, a photographic optical system used in an imaging device such as a digital camera or a video camera is required to be a zoom lens having a compact, wide field angle, high zoom ratio and high resolution. . In addition, in a photographic optical system used for a digital still camera, it has been desired to record not only a still image but also a moving image, and the entire system is a small lens system with high optical performance. It is requested.

  A so-called positive lead type zoom lens in which a lens group having a positive refractive power is disposed closest to the object side is known as a zoom lens having a small overall system and a high zoom ratio. As a positive lead type zoom lens, there is known a zoom lens having a four-group configuration composed of lens groups having positive, negative, positive, and positive refractive power in order from the object side (Patent Documents 1 and 2).

  Patent Document 1 proposes a compact zoom lens in which the first lens group is composed of one negative lens and one positive lens, and the second lens group is composed of two negative lenses and one positive lens. is doing. Patent Document 2 proposes a small zoom lens in which the first lens unit is monotonously moved toward the object side during zooming. In addition, as a positive lead type zoom lens, there is known a zoom lens having a five-group configuration including a lens group having positive, negative, positive, negative, and positive refractive power in order from the object side (Patent Document 3).

JP 2006-171055 A JP 2006-171655 A JP 2006-349947 A

  A positive lead type zoom lens is relatively easy to achieve a high zoom ratio while reducing the size of the entire system. In a positive lead type zoom lens, in order to reduce the size of the entire system while ensuring a predetermined zoom ratio, the number of lenses can be reduced while increasing the refractive power of each lens group constituting the zoom lens. . However, in such a zoom lens, the lens thickness increases as the refractive power of each lens surface increases. As a result, the shortening of the entire lens system becomes insufficient, and the occurrence of various aberrations increases.

  Further, in an image pickup apparatus that retracts and stores each lens group when the camera is not used, errors such as the tilting of the lens and the lens group inevitably increase due to the mechanical structure. At this time, if the sensitivity of the lens and the lens group is large, the optical performance is greatly deteriorated, and image distortion occurs during zooming.

  For this reason, it is necessary to obtain a high optical performance so that the sensitivity of the lens and the lens group is as small as possible.

  In the positive lead type 4 or 5 group zoom lens described above, in order to obtain high optical performance while reducing the size of the entire system and increasing the zoom ratio, the second and third lens groups are particularly preferred. It is important to set each element of the lens group appropriately. For example, it is important to appropriately set the zoom type (the number of lens groups and the refractive power of each lens group), the movement trajectory associated with zooming of each lens group, and the variable magnification burden of each lens group. .

  If these configurations are not appropriate, the entire system becomes large when a high zoom ratio is achieved, and variations in various aberrations associated with zooming increase, resulting in high optical performance over the entire zoom range and the entire screen. It becomes very difficult.

  An object of the present invention is to provide a zoom lens having good optical performance over the entire zoom range from the wide-angle end to the telephoto end and an image pickup apparatus having the same while achieving a high zoom ratio and a reduction in the effective diameter of the front lens. And

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and one or more lens groups. The first lens group moves in a convex locus toward the image side during zooming,
The second and third lenses so that the distance between the first lens group and the second lens group at the telephoto end is wider than the wide-angle end, and the distance between the second lens group and the third lens group is narrower. In a zoom lens in which the group moves, the third lens group has at least one positive lens and at least one negative lens;
The imaging magnifications at the wide-angle end and the telephoto end of the second lens group are β2w, β2T,
The imaging magnifications at the wide-angle end and the telephoto end of the third lens group are β3w, β3T,
The focal length of the second lens group is f2,
When the focal length of the entire system at the telephoto end is fT,
0.10 <(β2T / β2W) / (β3T / β3W) <1.65
0.01 <| f2 | / fT <0.15
It is characterized by satisfying the following conditions.

  According to the present invention, it is possible to obtain a zoom lens having excellent optical performance over the entire zoom range from the wide-angle end to the telephoto end while achieving a high zoom ratio and a reduction in the front lens effective diameter.

(A) (B) (C) (D) Cross-sectional views of the zoom lens of Example 1 at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end (A) (B) (C) (D) Aberration diagrams at the wide-angle end, first intermediate zoom position, second intermediate zoom position, and telephoto end of the zoom lens of Example 1. (A), (B), (C), and (D) Cross-sectional views of the zoom lens of Example 2 at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end. (A) (B) (C) (D) Aberration diagrams at the wide-angle end, first intermediate zoom position, second intermediate zoom position, and telephoto end of the zoom lens of Example 2. (A), (B), (C), and (D) Cross-sectional views of the zoom lens of Example 3 at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end. (A) (B) (C) (D) Aberration diagrams at the wide-angle end, first intermediate zoom position, second intermediate zoom position, and telephoto end of the zoom lens according to the third exemplary embodiment. Schematic diagram of main parts of an imaging apparatus of the present invention Schematic diagram of main parts of an imaging apparatus of the present invention

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The zoom lens of the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power (optical power = reciprocal of focal length), a second lens group having a negative refractive power, and a positive refractive power. The third lens group includes a rear group including one or more lens groups.

  During zooming from the wide-angle end to the telephoto end, the first lens unit moves while drawing a convex locus on the image side. In addition, the second lens group and the third lens group are arranged such that the distance between the first lens group and the second lens group at the telephoto end is wider than the wide angle end, and the distance between the second lens group and the third lens group is narrowed. Has moved.

  1A, 1B, 1C, and 1D show the wide-angle end (short focal length end), the first intermediate zoom position, the second intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 1 of the present invention. It is lens sectional drawing in an end (long focal length end). 2A, 2B, 2C, and 2D are aberration diagrams of the zoom lens of Embodiment 1 at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end, respectively. Example 1 is a zoom lens having a zoom ratio of 13.56 and an aperture ratio of about 3.40 to 6.21.

  3A, 3B, 3C, and 3D are lens cross-sectional views at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 2 of the present invention. is there. 4A, 4B, 4C, and 4D are aberration diagrams at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the second exemplary embodiment. The second embodiment is a zoom lens having a zoom ratio of 11.45 and an aperture ratio of about 3.50 to 5.73.

  5A, 5B, 5C, and 5D are lens cross-sectional views at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end of the zoom lens according to the third exemplary embodiment of the present invention. is there. FIGS. 6A, 6B, 6C, and 6D are aberration diagrams at the wide-angle end, the first intermediate zoom position, the second intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the third exemplary embodiment. The third embodiment is a zoom lens having a zoom ratio of 13.61 and an aperture ratio of about 2.88 to 6.00. FIG. 7 is a schematic diagram of a main part of a video camera (imaging device) including the zoom lens of the present invention. FIG. 8 is a schematic diagram of a main part of a digital still camera (image pickup apparatus) including the zoom lens of the present invention.

  The zoom lens of each embodiment is a photographic lens system used in an imaging apparatus such as a video camera, a digital still camera, a silver salt film camera, or a TV camera. In addition, the zoom lens of each embodiment can also be used as a projection optical system for a projection apparatus (projector). In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In the lens cross-sectional view, if i is the order of the lens group from the object side, Bi indicates the i-th lens group. LR is a rear group having one or more lens groups.

  SP is an aperture stop that determines (limits) a light beam having an open F number (Fno). The FP is a flare cut stop that does not require an aperture diameter, and cuts unnecessary light. G is an optical block corresponding to an optical filter, a face plate, a low-pass filter, an infrared cut filter, or the like. IP is the image plane. The image plane IP corresponds to an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor when a zoom lens is used as a photographing optical system of a video camera or a digital camera. When a zoom lens is used as a photographing optical system of a silver salt film camera, it corresponds to a film surface. Arrows indicate the movement trajectory of each lens unit during zooming (variation) from the wide-angle end to the telephoto end.

  In the aberration diagrams, Fno is the F number, ω is the half field angle, and the field angle based on the ray tracing value. In the spherical aberration diagram, the solid line is the d-line (wavelength 587.6 nm), and the two-dot chain line is the g-line (wavelength 435.8 nm).

  In the astigmatism diagram, the solid line and the dotted line are the sagittal image surface and the meridional image surface at the d line. Distortion is shown for the d-line. In the lateral chromatic aberration diagram, the two-dot chain line is the g-line. In each of the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens group is positioned at both ends of a range in which the zoom lens unit can move on the optical axis.

  In each example, in order from the object side to the image side, the first lens unit B1 having a positive refractive power, the second lens unit B2 having a negative refractive power, the third lens unit B3 having a positive refractive power, and 1 This is a zoom lens having a rear group LR having the above lens group. During zooming, the first lens unit B1 moves along a locus convex toward the image side. The second and third lenses are arranged such that the distance between the first lens group B1 and the second lens group B2 at the telephoto end is wider than the wide-angle end, and the distance between the second lens group B2 and the third lens group B3 is narrower. The group moves.

  In the first and second embodiments, the rear group LR includes a fourth lens unit B4 having a positive refractive power that moves during zooming.

  The third exemplary embodiment includes a fourth lens unit B4 having a negative refractive power that moves during zooming and a fifth lens unit B5 having a positive refractive power. However, in each embodiment, the number of lens groups constituting the rear group LR is arbitrary, and it is sufficient that at least one lens group is included.

  The aperture stop SP moves integrally with the third lens unit B3 during zooming.

  In the zoom lens of each embodiment, in order to ensure a high zoom ratio and correct aberrations, the first, second, and third refractive powers in order from the object side to the image side are positive, negative, and positive. The lens group is used. During zooming from the wide-angle end to the telephoto end, zooming is performed by increasing the distance between the first lens unit B1 and the second lens unit B2. Further, by moving the third lens unit B3 having the aperture stop SP, the entire system can be reduced in size by arbitrarily moving the entrance pupil at the telephoto end.

  Further, by moving the third lens unit B3 during zooming, the zooming action of the first lens unit B1 and the second lens unit B2 can be shared. Therefore, the amount of movement of the first lens unit B1 and the second lens unit B2 can be suppressed during zooming, and the total lens length (distance from the first lens surface to the image plane) at the telephoto end is shortened. .

  In zooming from the wide-angle end to the telephoto end, the zoom position at which the front lens effective diameter is the largest is the wide-angle end or a position slightly zoomed from the wide-angle end to the telephoto side. In order to bring the entrance pupil position closer to the object side from the image side at these zoom positions, the first lens unit B1 is moved in a convex locus toward the image side during zooming. By moving the first lens unit B1 toward the image side along a convex locus, the steep drop in the amount of light around the screen is reduced while reducing the effective diameter of the front lens.

  In each embodiment, the third lens unit B3 has at least one positive lens and at least one negative lens. By configuring the third lens unit B3 in this way, fluctuations in axial chromatic aberration during zooming due to an increase in the variable magnification load of the third lens unit B3 are suppressed.

  In each embodiment, the first lens unit B1 and the third lens unit B3 are located on the object side at the telephoto end compared to the wide-angle end. The first lens unit B1 moves along a locus convex toward the image side. Thereby, the effective diameter of the first lens unit B1 is reduced.

  In the zoom lens according to each embodiment, the distance between the first lens unit B1 and the aperture stop SP is reduced at the wide angle end by weakening the refractive power of the first lens unit B1 and increasing the refractive power of the second lens unit B2 to some extent. ing. Thus, the effective lens diameter of the first lens unit B1 is reduced. Further, the distance from the aperture stop SP to the image plane IP is reduced by increasing the refractive power of the third lens unit B3 to some extent. This shortens the total lens length at the wide-angle end.

  In the zoom lens according to each embodiment, the first lens unit B1 is moved to the object side at the telephoto end compared to the wide angle end. The zooming action is enhanced by increasing the distance between the first lens unit B1 and the second lens unit B2 at the telephoto end rather than at the wide angle end.

  Furthermore, the third lens unit B3 is moved to the object side during zooming from the wide-angle end to the telephoto end. The zooming effect is enhanced by narrowing the distance between the second lens unit B2 and the third lens unit B3 at the telephoto end as compared with the wide-angle end. In this way, by sharing the zooming action at a plurality of locations, the movement stroke of each lens unit for zooming is shortened while achieving a high zoom ratio. In particular, the total lens length is shortened at the telephoto end. In each embodiment, focusing from an object at infinity to an object at a short distance is performed by moving the final lens group to the object side. In Examples 1 and 2, focusing is performed by the fourth lens unit B4, and in Example 3, focusing is performed by the fifth lens unit B5.

  With the above configuration, the overall lens length is shortened and the zoom ratio is increased at the wide-angle end and the telephoto end.

  In Example 1 and Example 2, the flare-cut stop FP is provided between the third lens group B3 and the fourth lens group B4, thereby alleviating the sudden drop in the amount of light around the screen.

  In each embodiment, by adopting an aspherical lens in the third lens unit B3, spherical aberration and coma are favorably corrected on the wide angle side while ensuring a predetermined brightness.

  In Example 3, the use of an aspherical lens in the second lens unit B2 further improves the optical performance, and prevents the image surface from being tilted particularly at the wide angle side. In particular, it is more preferable that the image side lens surface of the negative lens closest to the object side in the second lens unit B2 has an aspherical shape in which the negative refractive power becomes weaker from the lens center toward the lens periphery.

  In each embodiment, the third lens unit B3 is moved so as to have a component perpendicular to the optical axis, thereby correcting blurring of the captured image when the entire optical system vibrates (tilts). Note that camera shake correction may be performed by moving an arbitrary lens group in a direction perpendicular to the optical axis.

  In each embodiment, the imaging magnifications at the wide-angle end and the telephoto end of the second lens unit B2 are β2w and β2T, respectively.

  The imaging magnifications at the wide-angle end and the telephoto end of the third lens unit B3 are β3w and β3T, respectively.

The focal length of the second lens unit B2 is f2, and the focal length of the entire system at the telephoto end is fT. At this time,
0.10 <(β2T / β2W) / (β3T / β3W) <1.65 (1)
0.01 <| f2 | / fT <0.15 (2)
Is satisfied.

  Conditional expression (1) is an expression that prescribes the variable magnification burden of the second lens unit B2 and the third lens unit B3. If the upper limit of the conditional expression (1) is exceeded and the zooming burden on the second lens unit B2 increases, the difference in the incident angle when the entire screen peripheral beam enters the refracting surface (lens surface) in the second lens unit B2 is a wide angle. Too large at the end and telephoto end. As a result, the change in field curvature due to zooming becomes large, and it becomes difficult to satisfactorily correct the field curvature over the entire zoom range.

  If the lower limit of the conditional expression (1) is exceeded and the zooming load of the third lens unit B3 becomes too large, the refractive power of the third lens unit B3 must be set large. At that time, the radius of curvature of each lens surface in the third lens unit B3 becomes small, and it becomes difficult to correct coma over the entire zoom range.

  Conditional expression (2) is an expression in which the focal length of the second lens unit B2 is defined by the focal length of the entire system at the telephoto end.

  If the upper limit of conditional expression (2) is exceeded and the focal length of the second lens unit B2 increases, the amount of movement of the first lens unit B1 during zooming increases when the zoom ratio is increased, and at the telephoto end. The total lens length increases, which is not preferable.

  If the lower limit of conditional expression (2) is exceeded and the focal length of the second lens unit B2 becomes too small, the Petzval sum increases in the negative direction and the field curvature increases, which is not preferable.

  If it is within the range of the conditional expression (1) and the conditional expression (2), the above-mentioned problem is unlikely to occur. Therefore, it is not necessary to add a new lens to the second lens group B2 or the third lens group B3 in order to increase the radius of curvature of each lens surface, and the number of lenses in each lens group can be reduced. It becomes easy to reduce the size of the system and maintain good optical performance. In each embodiment, it is more preferable that one or more of the following conditions be satisfied.

  Let nd3i, νd3i, and θgF3i be the refractive index, Abbe number, and partial dispersion ratio of the material of at least one positive lens of the positive lenses included in the third lens unit B3. The amount of movement on the optical axis in zooming from the wide-angle end to the telephoto end of the third lens unit B3 is m3. However, the movement amount m3 is the displacement amount (positional difference) of the lens group with respect to the image plane in the optical axis direction at the telephoto end compared to the wide angle end, and the sign is negative on the object side and positive on the image side. Let fW be the focal length of the entire system at the wide-angle end.

  Of the negative lenses included in the third lens unit B3, the focal length of at least one negative lens is f3n. Let the focal length of the third lens unit B3 be f3. Let the focal length of the first lens unit B1 be f1.

  The total lens length (air conversion distance from the first lens surface to the image plane) at the telephoto end is TDT, and the air conversion distance from the aperture stop SP to the image plane position at the telephoto end (distance when a parallel plate such as a filter is removed) Is a DSP.

At this time,
2.7 <β3T / β3W <5.0 (3)
1.54 <nd3i <2.0 (4)
55 <νd3i <100 (5)
0.5 <| m3 | / √ (fW × fT) <2.0 (6)
0.5 <f3 / √ (fW × fT) <1.5 (7)
0.1 <| f3n | / f3 <3.0 (8)
0.3 <DSP / TDT <0.8 (9)
0.2 <f1 / fT <1.2 (10)
−0.00162 × νd3i + 0.642 <θgF3i (11)
It is preferable to satisfy one or more of the following conditions.

  Next, the technical meaning of each conditional expression described above will be described.

  Conditional expression (3) defines the imaging magnification βT of the third lens unit B3 at the telephoto end by the imaging magnification β3W of the third lens unit B3 at the wide-angle end.

  If the upper limit of conditional expression (3) is exceeded and the zooming action of the third lens unit B3 becomes too large, it becomes difficult to correct spherical aberration and coma. Further, in order to increase the zooming action of the third lens unit B3, it is necessary to increase the refractive power of the third lens unit B3. If the refractive power of the third lens unit B3 is increased, the aberration sensitivity of the third lens unit B3 on the telephoto side increases, and the influence on manufacturing errors (lens eccentricity and tilting) increases, which is not preferable.

  If the lower limit of conditional expression (3) is exceeded and the zooming action of the third lens unit B3 becomes too small, it becomes difficult to achieve a high zoom ratio and downsizing the entire system. Further, since the zooming action of the third lens unit B3 is reduced, it is necessary to increase the zooming action of the second lens unit B2. At that time, it is necessary to increase the power (refractive power) of the second lens unit B2, or to increase the amount of movement of the second lens unit B2 during zooming. It becomes difficult to reduce the size of the system.

  Conditional expressions (4), (5), and (11) define a material that constitutes at least one positive lens included in the third lens unit B3.

Note that the Abbe number νd and the partial dispersion ratio θgF are Nd, NF, NC, and Ng when the refractive indices of the Fraunhofer d-line, F-line, C-line, and g-line are Nd, NF, NC, and Ng.
νd = (Nd−1) / (NF−NC)
θgF = (Ng−NF) / (NF−NC)
Defined by

  In each embodiment, by using a positive lens made of a material that simultaneously satisfies the conditional expressions (4), (5), and (11) for the third lens unit B3, primary achromaticity and secondary spectrum The correction is good.

  In Example 1 and Example 2, the seventh lens counted from the object side, and in Example 3, the sixth lens counted from the object side is made of a material that satisfies the conditional expressions (4), (5), and (11). .

  Conditional expression (4) defines the refractive index of the material of at least one positive lens included in the third lens unit B3.

  When the upper limit of conditional expression (4) is exceeded, the existing optical glass material tends to have a higher specific gravity as the refractive index is higher, which hinders weight reduction. For example, as in the first to third embodiments, when the third lens unit B3 is moved in the direction perpendicular to the optical axis to correct the shake of the captured image when the entire optical system vibrates (tilts), It is not preferable.

  When the lower limit of conditional expression (4) is exceeded, the refractive index of the positive lens material becomes too small, and the curvature of the lens surface of the positive lens must be increased. For this reason, a large low-order aberration coefficient is generated, and in particular, coma becomes large.

  Conditional expression (5) defines the Abbe number of the material of at least one positive lens included in the third lens unit B3, and defines conditions for minimizing axial chromatic aberration variation during zooming. Yes.

  Exceeding the lower limit of conditional expression (5) is not preferable because the variation in axial chromatic aberration during zooming becomes large and a large amount of chromatic aberration occurs on the telephoto side when a high zoom ratio is achieved.

  In each embodiment, the conditional expressions (4), (5), and (11) are satisfied at the same time, thereby facilitating a high zoom ratio while satisfactorily correcting the primary achromatic color and the secondary spectrum.

  Conditional expression (6) is an expression that defines the amount of movement of the third lens unit B3 during zooming, and is mainly for reducing the size of the entire lens system.

  When the amount of movement of the third lens unit B3 increases beyond the upper limit of the conditional expression (6), the change in the distance from the optical axes of the upper and lower lines of the beam around the screen at the wide angle end and the telephoto end in the third lens unit B3. growing. This makes it difficult to correct coma over the entire zoom range.

  If the lower limit of conditional expression (6) is exceeded, it becomes necessary to increase the amount of movement during zooming of the second lens unit B2 and increase the variable magnification load of the second lens unit B2. Then, the change in field curvature accompanying zooming becomes large, and it becomes difficult to satisfactorily correct the field curvature over the entire zoom range.

  Conditional expression (7) is an expression that prescribes the refractive power of the third lens unit B3, and is intended mainly for achieving a wide angle while satisfactorily suppressing spherical aberration and coma.

  If the upper limit of conditional expression (7) is exceeded and the refractive power of the third lens unit B3 becomes too weak, it is difficult to shorten the total lens length, which is not preferable. In addition, it becomes difficult to achieve a high zoom ratio.

  If the lower limit of conditional expression (7) is exceeded and the refractive power of the third lens unit B3 becomes too strong, widening of the angle becomes easy, but correction of spherical aberration and coma is difficult, which is not preferable.

  Conditional expression (8) relates to the focal length of at least one negative lens included in the third lens unit B3. When the upper limit of conditional expression (8) is exceeded, the refractive power of the negative lens included in the third lens unit B3 becomes weak, and it becomes difficult to shorten the total lens length of the third lens unit B3, which is not preferable.

  If the refractive power of the negative lens included in the third lens unit B3 becomes too strong beyond the lower limit of conditional expression (8), the overall lens length can be easily shortened, but the Petzval sum increases in the negative direction. This is not preferable because correction of curvature of field becomes difficult.

  Conditional expression (9) normalizes the aperture stop position in the lens system at the telephoto end.

  Exceeding the lower limit of conditional expression (9) is not preferable because the off-axis light beam of the first lens unit B1 moves away from the optical axis on the telephoto end side and the radial direction of the first lens unit increases.

  If the upper limit of conditional expression (9) is exceeded, the change in the distance from the optical axis of the peripheral luminous flux incident on the periphery of the screen of the lens group behind the aperture stop SP becomes large. As a result, in order to satisfactorily correct the aberration of the light beam around the screen, it is not preferable because the number of lenses is increased and a large number of aspheric surfaces are required.

  Exceeding the upper limit of conditional expression (10) is not preferable because the amount of movement of the first lens unit B1 or the second lens unit B2 necessary for zooming becomes large and it becomes difficult to shorten the total lens length.

  If the refractive power of the first lens unit B1 becomes too strong beyond the lower limit of the conditional expression (10), it is easy to shorten the total lens length at the telephoto end. The image shake at the time increases. As a result, a highly accurate lens barrel is required, which is not preferable.

  In each embodiment, it is desirable that the third lens unit B3 has at least one aspheric surface.

  It is desirable to use an aspherical surface in order to make the F number at the wide-angle end relatively small and to make the lens group of the rear group LR a simple lens configuration. In the first to third embodiments, at least one lens surface of the positive lens included in the third lens unit B3 is aspherical so that aberrations generated from the positive lens are suppressed to a low level. In other words, the aberration caused by the aspherical surface is balanced with the aberration caused by the aspherical surface by generating an aberration that is opposite to the aberration caused by the reference spherical surface of the positive lens.

  When the zoom lens of each embodiment is applied to an image pickup apparatus having an image pickup device, it is preferable to use circuit means for electrically correcting at least one of distortion and lateral chromatic aberration.

  In this way, if a lens configuration that can electrically permit distortion aberration caused by the zoom lens is used, the number of lenses of the zoom lens can be reduced, and the entire system can be easily downsized. In addition, by electrically correcting the chromatic aberration of magnification, it is possible to reduce the color blur of the captured image and to improve the resolution.

  In each embodiment, it is more preferable to set the numerical range of conditional expression (1) to conditional expression (10) as follows.

0.70 <(β2T / β2W) / (β3T / β3W) <1.65 (1a)
0.05 <| f2 | / fT <0.15 (2a)
2.7 <β3T / β3W <4.0 (3a)
1.54 <nd3i <1.80 (4a)
55 <νd3i <80 (5a)
0.6 <| m3 | / √ (fw × ft) <1.8 (6a)
0.6 <f3 / √ (fw × ft) <1.5 (7a)
0.2 <| f3n | / f3 <2.7 (8a)
0.3 <DSP / TDT <0.7 (9a)
0.4 <f1 / fT <1.2 (10a)
When the conditional expression (1a) is satisfied, the variable magnification sharing between the second lens unit B2 and the third lens unit B3 becomes more appropriate, and it becomes easy to suppress fluctuations due to field curvature and coma aberration zooming.

  By satisfying conditional expression (2a), it becomes easy to satisfactorily correct field curvature over the entire zoom range.

  By satisfying conditional expression (3a), it is easy to increase the zoom ratio and reduce the size.

  By satisfying conditional expression (4a), the lens configuration of the third lens unit B3 is simplified while correcting spherical aberration and coma.

  By satisfying conditional expression (5a), it becomes easy to further reduce the variation of axial chromatic aberration during zooming.

  By satisfying conditional expression (6a), the amount of movement of the third lens unit B3 during zooming becomes an appropriate amount, and it becomes easy to increase the zoom ratio and suppress coma.

  By satisfying conditional expression (7a), the refractive power of the third lens unit B3 becomes appropriate, and it becomes easy to increase the zoom ratio and shorten the total lens length at the telephoto end.

  By satisfying conditional expression (8a), it becomes easy to shorten the entire lens length and correct spherical aberration and coma.

  By satisfying the conditional expression (9a), it becomes easy to reduce the effective diameter of the front lens and correct the aberration of the off-axis light beam.

  By satisfying conditional expression (10a), it is easy to reduce the effective diameter of the front lens and correct axial chromatic aberration at the telephoto end.

  More preferably, the numerical range of conditional expression (1a) to conditional expression (10a) is set as follows.

1.00 <(β2T / β2W) / (β3T / β3W) <1.65 (1b)
0.10 <| f2 | / fT <0.15 (2b)
3.0 <β3T / β3W <4.0 (3b)
1.55 <nd3i <1.70 (4b)
60 <νd3i <80 (5b)
0.8 <| m3 | / √ (fw × ft) <1.5 (6b)
0.7 <f3 / √ (fw × ft) <1.0 (7b)
0.3 <| f3n | / f3 <2.4 (8b)
0.4 <DSP / TDT <0.6 (9b)
0.6 <f1 / fT <1.0 (10b)

Next, an embodiment of a camcorder (video camera) using the zoom lens of each embodiment as a photographing optical system will be described with reference to FIG. In FIG. 7, reference numeral 10 denotes a camera body, and 11 denotes a photographing optical system constituted by any zoom lens described in each embodiment. Reference numeral 12 denotes a solid-state imaging device (photoelectric conversion device) (imaging device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 11 and is built in the camera body 10. Reference numeral 13 is a finder for observing a subject image formed on the solid-state image sensor 12, which includes a liquid crystal display panel or the like. FIG. 8 is a schematic diagram of a main part of a digital still camera using the zoom lens of each embodiment. In FIG. 8, reference numeral 20 denotes a camera body, and reference numeral 21 denotes a photographing optical system constituted by any of the zoom lenses described in each embodiment. Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 21 and is built in the camera body 20.

  Hereinafter, specific numerical data of Numerical Examples 1 to 3 corresponding to Examples 1 to 3 will be shown. In each numerical example, i indicates the number of the surface counted from the object side. ri is the radius of curvature of the i-th optical surface (i-th surface). di is the axial distance between the i-th surface and the (i + 1) -th surface. ndi and νdi are the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. The two surfaces closest to the image correspond to the glass block G. The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, and A10 are aspherical surfaces. When using coefficients

It is expressed by the following formula. * Means a surface having an aspherical shape. “E−x” means 10 ^−x . BF is an air equivalent back focus. Table 1 shows the relationship between the above-described conditional expressions and numerical examples. Each numerical example shows values at the wide angle end, the first intermediate zoom position, the second intermediate zoom position, the four focal lengths F number at the telephoto end, the angle of view, the image height, the total lens length, the BF, and the like.
[Numerical Example 1]
Unit mm

Surface data surface number rd nd νd
1 44.910 1.10 1.80518 25.4
2 26.922 3.02 1.49700 81.5
3 213.269 0.20
4 29.723 2.42 1.69680 55.5
5 142.326 (variable)
6 597.524 0.80 1.88300 40.8
7 6.989 2.95
8 -19.693 0.65 1.71300 53.9
9 27.817 1.10
10 17.283 1.26 1.94595 18.0
11 100.561 (variable)
12 (Aperture) ∞ 1.97
13 * 5.868 2.60 1.55332 71.7
14 * -22.271 1.98
15 112.968 0.70 1.90366 31.3
16 4.627 0.23
17 5.315 2.20 1.58144 40.8
18 -599.875 0.60
19 ∞ (variable)
20 19.791 2.12 1.80 400 46.6
21 -29.812 0.70 1.84666 23.9
22 113.196 (variable)
23 ∞ 0.80 1.49831 65.1
24 ∞ 1.00
Image plane ∞

Aspherical data 13th surface
K = -2.94966e-002 A 4 = -2.56243e-004 A 6 = -3.86058e-006 A 8 = 5.95265e-007 A10 = -2.52991e-008

14th page
K = -2.14324e + 001 A 4 = 1.47358e-004 A 6 = 1.04081e-005

Various data Zoom ratio 13.56

Focal length 5.09 7.36 42.51 69.01
F number 3.40 3.71 5.01 6.21
Angle of view 35.02 27.85 5.50 3.25
Image height 3.55 3.88 3.88 3.88
Total lens length 59.51 58.11 75.78 83.01
BF 6.18 8.56 14.15 4.56

d 5 0.85 3.93 24.38 27.26
d11 20.70 14.18 2.02 2.00
d19 5.17 4.83 8.62 22.57
d22 4.64 7.02 12.62 3.03
d24 1.00 1.00 1.00 1.00

Zoom lens group data group Start surface Focal length
1 1 44.24
2 6 -7.34
3 12 14.01
4 20 31.01
5 23 ∞

[Numerical Example 2]
Unit mm

Surface data surface number rd nd νd
1 43.334 1.10 1.84666 23.9
2 27.386 2.82 1.49700 81.5
3 184.015 0.20
4 28.593 2.25 1.69680 55.5
5 129.921 (variable)
6 596.413 0.80 1.83481 42.7
7 6.794 3.15
8 -19.052 0.65 1.69680 55.5
9 27.361 0.92
10 16.564 1.26 1.94595 18.0
11 78.364 (variable)
12 (Aperture) ∞ 1.10
13 * 6.249 2.60 1.55332 71.7
14 * -20.019 1.32
15 22.644 0.70 1.80610 33.3
16 5.457 0.41
17 8.162 2.20 1.48749 70.2
18 35.340 0.60
19 ∞ (variable)
20 18.057 2.35 1.65844 50.9
21 -23.293 0.80 1.84666 23.9
22 -241.242 (variable)
23 ∞ 0.80 1.51633 64.1
24 ∞ 1.00
Image plane ∞

Aspherical data 13th surface
K = -2.10117e-002 A 4 = -3.88986e-004 A 6 = -6.43941e-006 A 8 = 4.92457e-007 A10 = -2.84254e-008

14th page
K = -9.71597e + 000 A 4 = 6.29353e-005 A 6 = 4.07868e-006

Various data Zoom ratio 11.45

Focal length 5.13 7.36 38.43 58.77
F number 3.50 3.78 5.10 5.73
Angle of view 34.98 27.99 6.40 3.90
Image height 3.55 3.88 3.88 3.88
Total lens length 58.20 56.74 72.70 80.10
BF 6.52 8.81 15.56 10.65

d 5 0.85 3.76 22.32 25.56
d11 20.70 14.42 2.39 1.49
d19 4.90 4.52 7.21 17.18
d22 4.99 7.28 14.03 9.12

Zoom lens group data group Start surface Focal length
1 1 43.47
2 6 -7.36
3 12 13.93
4 20 31.17
5 23 ∞

[Numerical Example 3]
Unit mm

Surface data surface number rd nd νd
1 35.277 1.00 1.94595 18.0
2 23.727 2.80 1.88300 40.8
3 133.434 (variable)
4 62.920 0.60 1.85135 40.1
5 * 7.437 4.11
6 -21.883 0.60 1.51680 64.2
7 13.179 0.30
8 11.709 1.93 1.94595 18.0
9 26.079 (variable)
10 (Aperture) ∞ 0.50
11 * 9.984 2.10 1.59201 67.0
12 11.375 0.80 1.94595 18.0
13 7.727 3.57 1.65844 50.9
14 * -19.364 (variable)
15 9.476 1.40 1.92286 20.9
16 6.882 (variable)
17 11.108 2.56 1.48749 70.4
18 -589.321 (variable)
19 ∞ 0.80 1.51680 64.2
20 ∞ 1.00
Image plane ∞

Aspheric data 5th surface
K = 1.29368e-001 A 4 = -1.88809e-005 A 6 = 4.74092e-007

11th page
K = -2.12053e-001 A 4 = -1.33629e-004 A 6 = 2.87874e-007 A 8 = -1.88648e-008

14th page
K = -1.10715e + 000 A 4 = 4.87229e-005

Various data Zoom ratio 13.61

Focal length 4.13 5.68 19.67 56.21
F number 2.88 3.01 4.13 6.00
Angle of view 36.24 32.00 10.38 3.56
Image height 3.10 3.60 3.60 3.60
Total lens length 61.21 54.10 65.20 87.96
BF 3.91 6.18 13.63 3.79

d 3 0.71 1.37 15.59 30.92
d 9 25.85 16.58 3.07 2.74
d14 2.86 3.24 4.84 6.03
d16 5.61 4.46 5.79 22.20
d18 2.38 4.66 12.10 2.27

Zoom lens group data group Start surface Focal length
1 1 55.84
2 4 -7.94
3 10 12.33
4 15 -36.76
5 17 22.40
6 19 ∞

B1 ... 1st lens group B2 ... 2nd lens group B3 ... 3rd lens group B4 ... 4th lens group B5 ... 5th lens group d ... d line g ... g line ΔM ... Meridional image plane ΔS ... Sagittal image plane SP ... Diaphragm FP ... Flare cut iris IP ... Imaging plane G ... Glass block of sensor face plate, low pass filter, etc. Spherical aberration ... Solid line: d line, two-dot chain line: g line
Astigmatism: Solid line: d-line ΔS, dotted line: d-line ΔM
Distortion ... d-line Magnification chromatic aberration ... Two-dot chain line: g-line

Claims (11)

In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear group including one or more lens groups. During zooming, the first lens unit moves along a locus convex toward the image side,
The second and third lenses so that the distance between the first lens group and the second lens group at the telephoto end is wider than the wide-angle end, and the distance between the second lens group and the third lens group is narrower. In a zoom lens in which the group moves, the third lens group has at least one positive lens and at least one negative lens;
The imaging magnifications at the wide-angle end and the telephoto end of the second lens group are β2W, β2T,
The imaging magnifications at the wide-angle end and the telephoto end of the third lens group are β3W, β3T,
The focal length of the second lens group is f2,
When the focal length of the entire system at the telephoto end is fT,
0.10 <(β2T / β2W) / (β3T / β3W) <1.65
0.01 <| f2 | / fT <0.15
A zoom lens characterized by satisfying the following conditions: The imaging magnifications β3W and β3T at the wide-angle end and the telephoto end of the third lens group are 2.7 <β3T / β3W <5.0.
The zoom lens according to claim 1, wherein the following condition is satisfied. When the refractive index and Abbe number of the material of at least one positive lens among the positive lenses included in the third lens group are nd3i and νd3i, respectively.
1.54 <nd3i <2.0
55 <νd3i <100
The zoom lens according to claim 1, wherein the following condition is satisfied. When the amount of movement on the optical axis in zooming from the wide-angle end to the telephoto end of the third lens group is m3, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT, respectively.
0.5 <| m3 | / √ (fW × fT) <2.0
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the third lens group is f3, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT, respectively.
0.5 <f3 / √ (fW × fT) <1.5
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of at least one negative lens among the negative lenses included in the third lens group is f3n and the focal length of the third lens group is f3, 0.1 <| f3n | / f3 <3.0
The zoom lens according to claim 1, wherein the following condition is satisfied.
The third lens unit has an aperture stop that moves integrally with the third lens unit at the object side during zooming. The total lens length at the telephoto end is TDT, and the air conversion from the aperture stop to the image plane position at the telephoto end. When the distance is DSP,
0.3 <DSP / TDT <0.8
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the first lens group is f1, 0.2 <f1 / fT <1.2
The zoom lens according to claim 1, wherein the following condition is satisfied.   The zoom lens according to any one of claims 1 to 8, wherein the rear group includes a fourth lens group having a positive refractive power, and the fourth lens group moves during zooming.   2. The rear group includes a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power, and the fourth lens group and the fifth lens group move during zooming. The zoom lens according to any one of 1 to 8.   An image pickup apparatus comprising: the zoom lens according to claim 1; and an image pickup element that receives an image formed by the zoom lens.